Synthesis and study of three novel macrocyclic selena[n]ferrocenophanes containing a naphthalene unit

Article abstract of DOI:10.1021/ic302628y

Three novel macrocyclic ligands, L1-L3, in which a ferrocene unit and a fluorescent moiety are linked to polyselena rings have been designed and prepared from 1,1′-bis(3-bromopropylseleno)ferrocene. Reaction of L with [M(NCMe)₄](PF₆)₂ (M = Pd and Pt) led to complexes [ML](PF₆)₂ (M = Pd and Pt). Crystal structure analysis revealed that after complexation, the macrocyclic ligand adopts the unusual c,c,c conformation due to intramolecular C-H?π interactions from the hydrogen atoms of ferrocene moieties to the naphthalene ring. Electrochemical studies showed that in [ML](PF₆)₂ (M = Pd and Pt) the half-wave potential of the 1,1′-ferrocenediyl group shifts to much more positive potentials due to electron density withdrawn from Se donor atoms. Electrochemical and optical measurements were used to calculate HOMO and LUMO levels as well as HOMO-LUMO band gaps. Results were compared and correlated with the differences in molecular structures.

Full text of DOI:10.1021/ic302628y

Article
pubs.acs.org/IC
Synthesis and Study of Three Novel Macrocyclic
Selena[n]ferrocenophanes Containing a Naphthalene Unit
Wei Ji,†,|| Su Jing,*,†,‡ Zeyu Liu,§ Jing Shen,† Jing Ma,*,§ Dunru Zhu,*,|| Dengke Cao,‡ Limin Zheng,‡
and Minxia Yao†
†College of Sciences, Nanjing University of Technology, Nanjing 211816, China
‡State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210008, China
§Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing
210093, China
||College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing
University of Technology, Nanjing 210009, China
S
* Supporting Information
ABSTRACT: Three novel macrocyclic ligands, L1−L3, in which a ferrocene unit and a fluorescent moiety are linked to
polyselena rings have been designed and prepared from 1,1′-bis(3-bromopropylseleno)ferrocene. Reaction of L with
[M(NCMe)4](PF6)2 (M = Pd and Pt) led to complexes [ML](PF6)2 (M = Pd and Pt). Crystal structure analysis revealed that
after complexation, the macrocyclic ligand adopts the unusual c,c,c conformation due to intramolecular C−H···π interactions
from the hydrogen atoms of ferrocene moieties to the naphthalene ring. Electrochemical studies showed that in [ML](PF6)2 (M
= Pd and Pt) the half-wave potential of the 1,1′-ferrocenediyl group shifts to much more positive potentials due to electron
density withdrawn from Se donor atoms. Electrochemical and optical measurements were used to calculate HOMO and LUMO
levels as well as HOMO−LUMO band gaps. Results were compared and correlated with the differences in molecular structures.
With these in mind, we are now undertaking a systematic
study of macrocyclic fluorophore-containing polyselena[n]-
ferrocenophanes with the target to sense late transition metal
ions. Systematic investigations have been reported on the
synthesis, structure, and property of polythia[n]ferrocenophane
by Sato and co-workers.2 After complexation, the dative Fe−M
bond was observed in some cases. In contrast, polyselena[n]-
ferrocenophanes have drawn less attention possibly due to the
difficulty of their preparation.2a Our lab has embarked upon
design of this class of ligands.3 As a result of the macrocyclic
effect, a suitable cavity size, and incorporation of soft donor Se
atoms, they have proven to coordinate well to late transition
metals. With incorporation of suitable signal units, they are also
INTRODUCTION
■
Design of functionalized receptors for development of potential
chemosensors is an area of intense activity. In this context, of
special interest is the design of multichannel-selective chemo-
sensors, which can lead to acquisition of multiple signal
expressions using single molecular entities. Toward this goal,
the receptors can be built by combining chromogenic units,
redox-active groups, or fluorescent signaling subunits near the
binding sites. This is an unfamiliar area because relatively few
examples describing coordination processes via multichannel
signaling have been reported.1 In addition, the mechanisms that
regulate the interaction between probes and their targets are
often poorly understood; hence, our ability to predict the
structural requirements and design new probes is limited. In
order to make perfect new receptor molecules, a better
understanding of the relevant interaction mechanisms will be of
significant help in a rational approach to such goals.
Received: November 30, 2012
© XXXX American Chemical Society
A
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Inorganic Chemistry
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at 0 °C; the solution turned purple in 5 min. Slowly warming to room
temperature, the color turned to yellow green, accompanying intense
H2 gas evolution. Two hours later, fc[Se(CH2)3Br]2 (195 mg, 0.3
mmol) in THF (10 mL) was then added slowly. The solution was left
to stir at room temperature for 3 h. Solvent was removed by
evaporation under reduced pressure. The residue was treated with
water (25 mL) and then extracted with CH2Cl2 (3 × 25 mL). The
extract was dried over MgSO4, evaporated to dryness, and then
subjected to column chromatography on SiO2. Elution with hexane/
dichloromethane (2:1) produced the target compound as an orange
expected to be efficient electrochemical and optical sensors for
late transition metal cations.
As a light-emitting fragment with strong emission and
chemical stability, the naphthalene unit has been widely
incorporated into chemosensors. From the viewpoint of
synthesis, peri-substituted naphthalenes have attracted more
and more attention due to the synthetic challenge and rigid C3
chelating property.4 The size and property of peri-atoms as well
as the number and size of atoms attached to them are
important. Heavier Group 16 (S, Se, Te) peri-substituted
naphthalenes shed light on unknown reactivity and possibly
development of a new concept of bonding.
In this paper, we presented the preparation, complexation,
and characterization of three novel macrocyclic polyselena[n]-
ferrocenophanes with a peri-substituted naphthalene unit. This
study is expected to provide a useful design strategy for
synthesis and application of multichannel sensors for late
transition metal ions.
1
solid. Yield: 107 mg (50%). H NMR (CDCl3): 7.81 (C10H6, H2+8, d,
2H), 7.74 (C10H6, H4+6, d, 2H), 7.32 (C10H6, H3+7, s, 4H), 4.22 (C5H4,
m, 8H), 3.24 (SeCH2CH2CH2, m, 8H), 2.21 (SeCH2CH2CH2, m,
4H). ES MS: 710 ([M]+).
Synthesis of L3. L3 was synthesized similar to L2, using
naphtho[1,8-c,d]-1,2-dithiole instead of naphtho[1,8-c,d]-1,2-disele-
nole. The target compound is obtained as an orange solid with a
1
yield of 60%. H NMR (CDCl3): 7.71 (C10H6, H2+8, d, 2H), 7.60
(C10H6, H4+6, d, 2H), 7.38 (C10H6, H3+7, s, 4H), 4.91 (C5H4, m, 8H),
3.50, 3.23 (CH2CH2CH2, m, 8H), 2.14 (SCH2CH2CH2, m, 4H). ES
MS: 618 ([M]+).
Synthesis of 1. PdCl2 (18 mg, 0.1 mmol) was refluxed in MeCN
(30 mL) for 2 h to give a yellow solution of [PdCl2(NCMe)2]. After
cooling, AgPF6 (51 mg, 0.2 mmol) was added and stirring continued
for another 15 min. L1 (74 mg, 0.1 mmol) in CH2Cl2 (5 mL) was then
added, and the mixture was stirred at room temperature for 24 h to
give a blue liquid and a fine white precipitate of AgCl. The mixture was
centrifuged to remove AgCl and reduced to 2 mL in vacuo. Diethyl
ether (10 mL) was added to precipitate the product as a blue powder.
Yield: 41 mg (48%). ES MS: 990.6 ([M − PF6]+).
EXPERIMENTAL SECTION
■
Materials and General Procedures. All reactions below were
carried out under nitrogen using standard Schlenk techniques. All
solvents were distilled from elemental alkali metal or Na/K alloy,
except ethanol (which was degassed before use), acetonitrile, and
dichloromethane (which were distilled over calcium hydride). fcSe3
and fc[Se(CH2)3Br]2 were prepared following the previously reported
method.3c,5
Physical Measurements. Mass spectra were recorded using
electron impact (EI) or positive-ion electrospray (ES): m/z values
have been rounded to the nearest integer or half-integer; assignments
Synthesis of 2−6. Synthesis was similar to 1. 2: brown powder. ES
MS: 1072.3 ([M − PF6]+). 3: brown black powder. ES MS: 964.4 ([M
− PF6]+). 4: brown powder. ES MS: 1050.7 ([M − PF6]+). 5: black
powder. ES MS: 866.7 ([M − PF6]+), 362.3 ([M − 2PF6]2+). 6: brown
powder. ES MS: 956.7 ([M − PF6]+), 406.3 ([M − 2PF6]2+).
X-ray Data Collection and Structure Determinations.
Structural determinations were performed on a Bruker SMART
APEX II CCD diffractometer using graphite-monochromatized Mo Kα
radiation (λ = 0.71073 Å) at room temperature. A hemisphere of data
was collected using a narrow-frame method with scan widths of 0.30°
in ω and an exposure time of 10 s/frame. Data were integrated using
the Siemens SAINT program,6 with intensities corrected for Lorentz
factor, polarization, air absorption, and absorption due to variation in
the path length through the detector faceplate. Multiscan absorption
corrections were applied. Structures were solved by direct methods
and refined on F2 by full-matrix least-squares using SHELXTL.7 All
non-hydrogen atoms were located from the Fourier maps and refined
anisotropically. All H atoms were refined isotropically, with the
isotropic vibration parameters related to the non-H atom to which
they are bonded. Relevant details for structure refinements of L1−L3,
1·CH3CN·H2O, 3, 5, and 6 are listed in Tables 1 and 2. Selected bond
lengths and angles are given in the Supporting Information (Tables S1
and S2). CCDC 910592−910598 contain supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
from the Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
Theoretical Calculations. All density functional theory (DFT)
calculations were performed with the Gaussian 09 program package.8
Geometrical structures of L1, L2, and 1−4 were fully optimized using
the 6-31+G(d,p) basis set for nonmetal atoms (except for Se) and
LanL2DZ basis set for metal and Se atoms. All structures were
characterized as local minima by vibrational frequency analyses.
Vertical excitation energies were obtained by time-dependent density
functional theory (TDDFT) at the same level as geometry
optimizations. The 6-31+G(d,p) rather than LanL2DZ basis set was
used for Pd and Se atoms in TDDFT calculations of L3, 5, and 6 to
get the converged results. Natural bond orbital (NBO) calculations
were performed to estimate the interaction energy between the
orbitals.
are based on isotopomers containing H, 12C, 56Fe, 80Se, and 106Pd or
1
195Pt; expected isotope distribution patterns were observed. H NMR
1
spectra were measured in CDCl3 at room temperature with a Varian
Unity Plus 400 MHz NMR spectrometer. UV−vis absorption spectra
were measured with a Varian UV−vis spectrophotometer. Fluo-
rescence spectra were recorded at room temperature on a Horiba
fluoromax-4 fluorescence spectrometer. For all measurements,
excitation was at 287 nm. Both excitation and emission slit widths
were 1.6 nm. Electrochemical measurements were performed at room
temperature in a dry acetonitrile solution containing 0.1 M
[NBu4][PF6] electrolyte using an CHI 660C potentiostat system.
The sweep rate for cyclic voltammetry was 100 mV s−1. A three-
electrode arrangement was used with a Pt working electrode, a Pt wire
counter electrode, and a Ag/Ag+ (0.01 M AgNO3 in CH3CN,
referenced against ferrocene/ferrocenium) reference electrode. The
sweep rate for cyclic voltammetry was 100 mV s−1. A three-electrode
arrangement was used with a Pt working electrode, a Pt wire counter
electrode, and a Ag/Ag+ (0.01 M AgNO3 in CH3CN, referenced
against ferrocene/ferrocenium) reference electrode.
Synthesis of L1. NaBH4 (46 mg, 1.2 mmol) was added to an
ethanol solution of 1,8-bis(selenocyanatomethyl)naphthalene (109
mg, 0.3 mmol) at 0 °C; the solution turned yellow in 5 min. Slowly
warming to room temperature, the color disappeared quickly,
accompanying intense H2 gas evolution. fc[Se(CH2)3Br]2 (176 mg,
0.3 mmol) in THF (5 mL) was then added slowly. The solution was
left to stir at room temperature for 3 h. Solvent was removed by
evaporation under reduced pressure. The residue was treated with
water (25 mL) and then extracted with CH2Cl2 (3 × 25 mL). The
extract was dried over MgSO4, evaporated to dryness, and then
subjected to column chromatography on SiO2. Elution with hexane/
dichloromethane (3:1) produced the target compound as a yellow
1
solid. Yield: 35 mg (16%). H NMR (CDCl3): 7.76 (C10H6, d, 2H),
7.54 (C10H6, d, 2H), 7.38 (C10H6, s, 4H), 4.71 (SeCH2, s, 4H), 4.29
(C5H4, m, 8H), 3.06 (SeCH2CH2CH2, m, 8H), 2.25 (SeCH2CH2CH2,
m, 4H). ES MS: 738 ([M]+).
Synthesis of L2. NaBH4 (46 mg, 1.2 mmol) was added to an
ethanol solution of naphtho[1,8-c,d]-1,2-diselenole (86 mg, 0.3 mmol)
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As rigid C3 ligands, naphthalene imposes strain on non-
hydrogen peri-atoms, which forces the two peri-atoms to form
sub van der Waals contacts. Strain can also make nonbonded
peri-substituted systems to distort from the idealized geometry
in the naphthalene either by splaying, i.e., C−C−E angles
varying from 120°, or by the naphthalene backbone becoming
nonplanar.9 Structures of L1−L3 all obey this rule; the atoms
attached on the naphthalene unit are displaced above and
below the planes of the naphthalene backbones; this deviation
decreases in the sequence Se > S > C.
Table 1. Crystal Data and Structure Refinement Details of
L1−L3
L1
L2
L3
formula
C28H30FeSe4
738.21
C26H26FeSe4
710.16
C26H26FeS2Se2
616.36
fw
temp (K)
cryst size (mm3)
293(2)
293(2)
296(2)
0.80 × 0.80 ×
0.40
0.70 × 0.60 ×
0.30
0.30 × 0.20 ×
0.15
cryst syst
triclinic
orthorhombic
orthorhombic
space group
a/b/c (Å)
P-1
P212121
Pbca
In L1, the ferrocene unit adopts a “synclinal eclipsed”10
conformation with a torsion angle C1−X1−X2−C6 of 69.3(2)°
(X1 and X2 are the centroids of the two Cp rings). The nearest
neighboring asymmetric units are connected to each other to
form a dimer through intermolecular C−H···Se hydrogen
bonds and the C−H···π interactions from the hydrogen atoms
of ferrocene moieties to the naphthalene rings. These dimers
further interact along the a axis to form a one-dimensional
chain by weak hydrogen bonds (see Figure S1, Supporting
Information).
9.099(2)/
10.769(3)/
14.734(4)
10.544(2)/
14.235(2)/
31.750(5)
19.22(1)/
11.52(1)/
21.88(1)
α/β/γ (deg)
73.561(4)/
77.913(4)/
70.602(5)
90/90/90
90/90/90
V (Å3)
1295.4(6)
2
4766(1)
8
4846(5)
8
Z
Dcalcd (Mg m−3
)
1.893
1.980
1.690
F(000)
μ (mm−1
720
2752
2464
)
6.217
6.756
3.812
The asymmetric unit of L2 comprises two molecules with
different configurations. One ferrocene unit adopts a “synclinal
eclipsed” conformation with a torsion angle C31−X1−X2−C36
of 61.0(4)°, and atoms C24 and C25 in one trimethylene chain
are highly disordered with an occupancy of 0.60. Another
adopts “synperiplanar” conformation with a torsion angle C1−
X1−X2−C6 of 2.0(3)°, along with intramolecular C−H···π
interactions from the hydrogen atoms of ferrocene moieties to
the naphthalene ring. In both configurations peri-selenium
distances (3.162 or 3.147 Å) are comparable with those in
analogous cyclic tetraselenide 8,9,19,20-tetrahydrodinaphtho-
[1′,8′-jk:1,8-bc][1,5,9,13]tetraselenacyclohexadecine (3.167,
3.194 Å).3a
θ range (deg)
h/k/l
2.06−25.00
1.92−27.10
1.86−25.00
−10, 6/−12,12/ −13, 12/−10,18/ −22,22/−
−17,14 −40,40 12,13/−25,26
no. of reflns
collected
6494 27 730 32 329
no. of indep reflns 4502 [0.0245]
[Rint]
10 496 [0.0601]
7894
4265 [0.0571]
3298
no. of obsd reflns 3586
[I > 2σ(I)]
data/restraints/
params
4502/0/314
10496/7/578
4265/0/280
GOF
1.084
1.016
1.088
R1, wR2 indices [I 0.0268, 0.0537
> 2σ(I)]
0.0407, 0.0717
0.0294, 0.0625
R1, wR2 indices
(all data)
0.0354, 0.0547
0.0656, 0.0762
0.0471, 0.0663
In L3, the ferrocene unit adopts a “synperiplanar”
conformation with a torsion angle C1−X1−X2−C6 of
3.1(2)°. The nonbonded S···S distance is 3.066 Å, shorter
than that in [1,8-b,c]-1,5-dithiocin (3.227(1) Å).11
largest diff. peak
0.323, −0.470
1.005, −0.673
0.273, −0.402
and hole (eÅ−3
)
On the other hand, the intramolecular Se1···Se2 distance
(attached on Cp ring) (L1, 4.846 Å; L2, 3.855 and 4.562 Å; L3,
3.636 Å) is much shorter than that (5.200(2) Å) in fcSe4.3a
After complexation, the metal atom is coordinated by the
macrocyclic ligand in a slightly distorted square planar
geometry and deviates from the best plane through four
donor atoms by 0.21 (1·CH3CN·H2O) and 0.01 Å (3, 5, 6). In
the solid state structures of these complexes the macrocyclic
ligand adopts the c,c,c conformation.12 Two trimethylene-
chelate six-membered rings have the chair conformation. The
same macrocyclic stereochemistry was observed in the solid
state structure of [M({16}aneSe4)](BF4)2 (M = Pd or Pt),13
whereas the c,t,c conformation was found for [M({16}aneSe4)]-
(PF6)2·2MeCN and [M(fcSe4)](PF6)2 (M = Pd or Pt).14,3a The
present c,c,c arrangements can be attributed to intramolecular
C−H···π interactions from the hydrogen atoms of ferrocene
moieties to the naphthalene ring. D···A distances of C−H···π
bonds range from 3.74 to 4.36 Å (Figure 1 and Table 3). The
dihedral angle between the two planes (best plane through four
donor atoms and the naphthalene ring) is 60.4°, 72.3°, 68.7°,
and 68.9° for 1·CH3CN·H2O, 3, 5, and 6, respectively.
In each complex, the Se(S)−M−Se(S) (M = Pd and Pt)
angles formed by the ferrocene and naphthalene unit are
smaller than those formed by the trimethylene chains. Possibly,
geometric requirements for optimization of the overlap
between the Se(S) lone pairs and M orbitals play an important
RESULTS AND DISCUSSION
Synthesis. L1−L3 were synthesized in a stepwise manner,
■
as shown in Scheme 1. For L1, reduction of 1,8-bis-
(selenocyanatomethyl)naphthalene with NaBH4 afforded rela-
tive dianion, which was then reacted with 1,1′-bis(3-
bromopropylseleno)ferrocene, fc[Se(CH2)3Br]2 (fc = [Fe(η5-
C5H4)2]), to give the target compound via [1 + 1] cyclization.
L2 and L3 were obtained using naphtho[1,8-c,d]-1,2-diselenole
or naphtho[1,8-c,d]-1,2-dithiole instead of 1,8-bis-
(selenocyanatomethyl)naphthalene.
Addition of 1 equiv of L in CH2Cl2 to a solution of
[M(NCMe)4](PF6)2 in acetonitrile at room temperature gave a
dark blue (M = Pd) or red (M = Pt) liquid, from which
[ML](PF6)2 could be precipitated by addition of diethyl ether
(1 M = Pd, L = L1; 2 M = Pt, L = L1; 3 M = Pd, L = L2; 4 M =
1
Pt, L = L2; 5 M = Pd, L = L3; 6 M = Pt, L = L3). H NMR
spectra of L reveal the expected resonances. Mass spectra of L
and complexes exhibit the correct isotopic patterns for the
proposed formulas.
Crystallographic Study. Single crystals of L1−L3 suitable
for X-ray diffraction study were obtained as orange plates from
CH2Cl2/hexanes. Crystals suitable for single-crystal X-ray
analyses of the four complexes, 1·CH3CN·H2O, 3, 5, and 6,
were obtained by slow diffusion of Et2O into a solution in
MeCN. Structures are shown in Figure 1.
C
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Table 2. Crystal Data and Structure Refinement Details of 1, 3, 5, and 6
1·CH3CN·H2O
3
5
6
formula
C30H35F12FeNOP2PdSe4
1193.62
C26H26F12FeP2PdSe4
1106.50
C26H26F12FeP2PdS2Se2
1012.70
C26H26F12FeP2PtS2Se2
1101.39
fw
temp (K)
cryst size (mm3)
cryst syst
space group
a/b/c (Å)
293(2)
293(2)
296(2)
296(2)
0.5 × 0.5 × 0.5
triclinic
0.20 × 0.10 × 0.10
triclinic
0.10 × 0.08 × 0.07
triclinic
0.20 × 0.15 × 0.10
triclinic
P-1
P-1
P-1
P-1
11.855(1)/13.128(1)/
13.184(1)
10.676(2)/11.868(2)/
13.387(2)
10.529(4)/11.795(4)/
13.352(5)
10.549(7)/11.809(8)/
13.322(9)
α/β/γ (deg)
84.566(2)/67.686(2)/
80.060(2)
75.271(3)/78.638(3)/
83.311(3)
75.373(4)/78.897(4)/
83.309(4)
75.320(8)/78.846(8)/
82.675(8)
V (Å3)
1868.7(3)
2
1604.4(5)
2
1570.5(10)
2
1569.5(19)
2
Z
Dcalcd (Mg m−3
)
2.121
2.290
2.142
2.330
F(000)
μ (mm−1
1152
1056
984
1048
)
4.939
5.740
3.679
7.560
θ range (deg)
h/k/l
2.26−25.00
−8, 14/−15,15/−11,15
9383
1.95−25.00
−12, 12/−14,13/−12,15
7926
1.60−25.00
−12,11/−13,13/−15,15
11 206
1.60−25.00
−12,12/−13,14/−15,15
10 846
no. of reflns collected
no. of indep reflns [Rint]
no. of obsd reflns [I > 2σ(I)]
data/restraints/params
GOF
6477 [0.0352]
5099
5549 [0.0234]
4615
5463 [0.0268]
4439
5439 [0.0303]
4295
6477/0/469
1.042
5549/0/415
1.003
5463/0/415
1.082
5439/0/415
1.018
R1, wR2 indices [I > 2σ(I)]
R1, wR2 indices (all data)
largest diff. peak and hole
0.0391, 0.0992
0.0490, 0.1018
1.214, −0.595
0.0552, 0.1664
0.0647, 0.1743
2.008, −1.751
0.0384, 0.1094
0.0491, 0.1149
1.026, −0.703
0.0364, 0.0970
0.0525, 0.1027
1.257, −0.968
(eÅ−3
)
Scheme 1. Synthetic Routes of L1−L3
role here in addition to the major constraint posed by the
dimension of the ferrocene and naphthalene unit.
After complexation, the ferrocene group in [ML](PF6)2 (M
= Pd and Pt) adopts a “synperiplanar” conformation. The
Fe···M distance is 4.073(1) Å for 1·CH3CN·H2O, 3.902(1) Å
for 3, 3.879(1) Å for 5, and 3.887(2) Å for 6. These distances
are larger than the sum of the covalent radii of both metal
atoms.
The half-wave potentials for oxidation of the ferrocene
moiety of L are all larger than that of fcSe4 (32 mV), which
mean it is more difficult to oxidize. Cyclic voltammograms of
[ML](PF6)2 show one quasi-reversible redox wave from 642 to
784 mV in the potential range from −0.5 to +1.0 V. This is
assigned to oxidation of the ferrocene moiety, as oxidation or
reduction of the M(II) center occurs outside this potential
range. There is a large positive potential shift in E1/2 compared
to the free ligand; ΔE is in the range from 580 to 716 mV (see
Figure 2 and Figure S2, Supporting Information). Changing the
metal from Pd to Pt did not bring about a significant change in
Electrochemical Study. The redox behavior was inves-
tigated by cyclic voltammetry (CV) in acetonitrile solution, and
data obtained are summarized in Table 4.
D
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Figure 1. View of the structures with 30% probability ellipsoids. Less populated fraction of the disordered chain is shown with dashed bonds.
Hydrogen atoms except hydrogen-bonding interactions are omitted for clarity.
a
Table 3. Intramolecular Hydrogen-Bonding Interactions
D−H···A
Cg1
d(D−H)/Å
d(H···A)/Å
d(D···A)/Å
∠DHA/deg
L2
1
C31−H31···Cg1
C36−H36···Cg1
C5−H5A···Cg1
C10−H10···Cg1
C5−H5···Cg1
C10−H10···Cg1
C5−H5A···Cg1
C10−H10A···Cg1
C5−H5A···Cg1
C10−H10A···Cg1
C44−C45−C46−C47−C48−C49
C40−C41−C42−C43−C44−C49
C19−C20−C21−C22−C23−C24
C15−C16−C17−C18−C19−C24
C18−C19−C20−C21−C22−C23
C14−C15−C16−C17−C18−C23
C18−C19−C20−C21−C22−C23
C14−C15−C16−C17−C18−C23
C18−C19−C20−C21−C22−C23
C14−C15−C16−C17−C18−C23
0.93
0.93
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
3.08
2.75
2.97
2.79
3.09
3.38
3.35
3.09
3.35
3.11
3.86
3.50
3.82
3.74
4.05
4.36
4.32
4.06
4.32
4.09
142.7
138.7
145.6
161.8
169.0
171.7
170.9
169.7
171.6
171.7
3
5
6
a
Cg1 is the centroid of the naphthalene unit.
Table 4. Cyclic Voltammetric Data for L and Complexes
a
M···Fe (Å)
E1/2 (|Epa− Epc|) (mV)
ΔE1/2 (mV)
L1
1
103 (171)
683 (113)
696 (142)
53 (98)
4.073(1)
580
593
b
2
4.251
L2
3
3.9013(3)
642 (119)
664 (257)
68 (215)
766 (124)
784 (174)
589
611
b
4
4.334
L3
5
3.879 (1)
3.887 (2)
698
716
6
a
b
E1/2 values are quoted relative to FcH /[FcH]+. Calculated at the
PBE1PBE level.
Figure 2. Cyclic voltammograms of L1 and 1 in dry acetonitrile, 0.1 M
[NBu4][PF6], at a scan rate of 100 mV s−1.
electrochemical behavior. Several literature works proved that
the ferrocenyl group can act as a donor in the coordination
sphere of the metal cation or behave as a moderately strong
base toward the metal cation.15 However, in current cases, the
large Fe···M (Pd or Pt) distance (about 400 pm) gives a slim
chance for direct interaction.
A previous study shows that selenoxide or sulfoxide formed
on the electrochemical oxidation of Se (or S) peri-substituted
naphthalenes. These phenomena were also observed in L2 and
L3 (see Figures S3 and S4, Supporting Information), which can
be attributed to removal of an electron from the occupied
molecular orbitals, which is Se (or S) lone pair in character
followed by attack by residue water in the acetonitrile solvent.16
Computational Results. To seek more detailed informa-
tion on the electronic structures of the host−guest complex-
ation, the geometries of L1, L2, and 1−4 were optimized by
E
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Inorganic Chemistry
Article
DFT calculations (cf. Theoretical Calculations). Then, the
electronic structural properties were evaluated using the same
basis sets at the optimized geometries. Optimized geometries
are in agreement with the above-mentioned experimental X-ray
structures of 1 and 3. Three kinds of functionals, B3LYP,
B3PW91, and PBE1PBE, were used for absorption of L1
(Figure 3). Among them, PBE1PBE results are in better
the electronic structure properties described below (Figures
5−7). The conformational superpositions of the optimized and
crystal structures of complexes 1 and 3 show a qualitative
agreement between them.
TD-DFT calculation results show that, in free ligands, the
maximum absorption wavelength corresponds to the transition
between the π-type HOMO-4 and the π*-type LUMO, mainly
localized on the naphthalene unit (Figure 5). After complex-
ation, the maximum absorption is dominated by the transition
between the metal-centered d orbital and the naphthalene-
centered π*-type unoccupied molecular orbital, i.e., the metal-
to-ligand charge transfer (MLCT).
The energy levels of the HOMO and LUMO orbitals are all
upshifted with introduction of a metal atom to the ligands
(Figure 6). Moreover, the energy level of the HOMO displays a
significant exaltation by comparison to that of the LUMO.
Consequently, the energy gap between the LUMO and the
HOMO is markedly narrowed after complexation. It can be
found from the natural bond orbital analysis that there is no
evident interaction between the d orbitals of Fe and Pd atom
(Table S4, Supporting Information). Occupation of each d
orbital of Pd is close to 2, and the Fe−Pd interaction energy is
close to zero, which is much less than that of Fe−C interaction
(about 339 kcal/mol) in the ferrocene moiety. The negligible
interaction between the Fe and the Pd atoms is consistent with
the large Fe···Pd distance (about 400 pm) of them in the crystal
structures. The remarkable perturbation of the redox wave of
the ferrocene/ferrocenium redox couple can only be attributed
to electron density withdrawn from the Se donor atoms after
complexation.
Figure 3. Absorption spectra and related molecular orbitals of L1
obtained using different functionals.
agreement with experimental data than the others. PBE1PBE
was then chosen to optimize geometries (Figure 4) and study
Figure 4. Optimized geometries of 1−4 at the PBE1PBE level (bond lengths are given in Angstroms and angles in degrees), and geometrical
parameters of the X-ray structure (shown in thin lines) are given in parentheses for comparison.
F
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Figure 5. Absorption spectra and related molecular orbitals of metallocenes (L1 and L2) and their Pd complexes (1 and 3) obtained from
experiential observation and TD-DFT/PCM calculation.
Figure 6. Energies of the HOMO and LUMO of various metallocenes calculated using the PBE1PBE functional (selection of basis sets for L3 and 5
can be found in Theoretical Calculations).
The computed energy levels of the HOMO and LUMO as
well as the HOMO−LUMO gap also agree well with those
detected from cyclic voltammetry (Table S3, Supporting
Information). The HOMO is determined according to the
equation EHOMO = −(4.8 − Eref + Eox, onset) eV, where Eox,onset is
the potential at the onset of oxidation and Eref is the potential of
the ferrocene reference.17 The value of optical band gap is
determined by the absorption onset obtained from the UV−vis
absorption spectrum. The LUMO level is estimated by adding
the optical band gap to the HOMO value. As shown in Figure
7, good agreement is found between the experimental
observation and the theoretical investigation.
It should be mentioned that the study of the fluorescence
behavior was carried out in acetonitrile solution. When excited
at 287 nm, the ligands show typical structured naphthalene-like
emission spectra at 329 nm (see Figure S6, Supporting
Information). Complexes with Pd2+ and Pt2+ were not
luminescent; the close proximity of the metal ions to the
fluorophore provides pathways for energy- and electron-transfer
processes, which cause fluorescence quenching.
CONCLUSIONS
■
This paper presents the synthesis and characterization of three
novel macrocyclic polyselenaferrocenophanes containing a
naphthalene unit and six Pd(II), Pt(II) complexes. X-ray
crystallographic studies confirm that Pd(II) and Pt(II) ions are
able to insert into the cavity of L to yield complexes with a
square planar coordination geometry, with the ligand adopting
a c,c,c configuration. Cyclic voltammetry shows that E1/2 of the
1,1′-ferrocenediyl group shifts to more positive potentials in
[ML](PF6)2 (M = Pd and Pt). The HOMO and LUMO levels
were determined by experiments and theory calculations.
Natural bond orbital analysis shows that there is no overlap
between the d orbitals of Fe and the M atom. Consequently, no
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Article
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Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;
direct Fe···Pd interaction exists in these complexes. We expect
that our results and elaborations may provide a useful and
pioneering guide to designing a new multichannel molecular
sensor.
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures, characterization data for synthesis,
crystal data, calculated information, and X-ray structural data
for CCDC 910592−910598 in CIF format. This material is
available free of charge via the Internet at http://pubs.acs.org.
̈
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.;
Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,
revision A.02; Gaussian, Inc.: Wallingford, CT, 2009.
(9) Aucott, S. M.; Milton, H. L.; Robertson, S. D.; Slawin, A. M. Z.;
Woollins, J. D. Heteroatom Chem. 2004, 15, 530.
(10) Fujihara, H.; Yabe, M.; Ilemori, N.; Furukawa, N. J. Chem. Soc.,
AUTHOR INFORMATION
Corresponding Author
*Phone: +86-25-58139150 (S.J.); +86-25-83597408 (J.M.);
+86-25-83587717 (D.Z.). Fax: +86-25-58139149 (S.J.); +86-
25-83596131 (J.M.); +86-25-83172261 (D.Z.). E-mail: sjing@
njut.edu.cn (S.J.); majing@mail.nju.edu.cn (J.M.); zhudr@njut.
edu.cn (D.Z.).
■
Perkin Trans. 1 1993, 2145.
(11) Glass, R. S.; Andruski, S. W.; Broeker, J. L.; Firouzabadi, H.;
Steffen, L. K.; Wilson, G. S. J. Am. Chem. Soc. 1989, 111, 4036.
(12) Panda, A. Coord. Chem. Rev. 2009, 253, 1056.
(13) Batchelor, R. J.; F. Einstein, W. B.; Gay, I. D.; Gu, J. H.; Pinto, B.
M.; Zhou, X. Inorg. Chem. 1996, 35, 3667.
Notes
(14) Champness, N. R.; Kelly, P. F.; Levason, W.; Reid, G.; Slawin, A.
M. Z.; Williams, D. Inorg. Chem. 1995, 34, 651.
The authors declare no competing financial interest.
(15) (a) Akabori, S.; Kumagai, T.; Shirahige, T.; Sato, S.; Kawazoe,
K.; Tamura, C.; Sato, M. Organometallics 1987, 6, 2105. (b) Medina, J.
C.; Goodnow, T. T.; Rojas, M. T.; Atwood, J. L.; Lynn, B. C.; Kaifer,
ACKNOWLEDGMENTS
■
We gratefully acknowledge financial support from the National
Natural Science Foundation (Grant Nos. 21171092, 21171093,
20825312, and 21273102) and Foundation of State Key
Laboratory of Materials-Oriented Chemical Engineering, NJUT
(Grant No. KL12-06).
A. E.; Gokel, G. W. J. Am. Chem. Soc. 1992, 114, 10583. (c) Oton
Ratera, I.; Espinosa, A.; Wurtz, K.; Parella, T.; Tarraga, A.; Veciana, J.;
Molina, P. Chem.Eur. J. 2010, 16, 1532. (d) Caballero, A.; Tormos,
R.; Espinosa, A.; Velasco, M. D.; Tarraga, A.; Miranda, M. A.; Molina,
P. Org. Lett. 2004, 6, 4599.
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, F.;
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(16) (a) Glass, R. S.; Andruski, S. W.; Broeker, J. L.; Firouzabadi, H.;
Steffen, L. K.; Wilson, G. S. J. Am. Chem. Soc. 1989, 111, 4036.
(b) Fujihara, H.; Yabe, M.; Ilemori, M.; Furukawa, N. J. Chem. Soc.
Perkin Trans. 1 1993, 2145. (c) Fujihara, H.; Yabe, M.; Furukawa, N. J.
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Sensfuss, S. Sol. Energ. Mater. Sol. C 2005, 85, 13. (b) Pommerehne, J.;
Vestweber, H.; Guss, W.; Mahrt, R. F.; Porsch, M.; Daub, J. Adv.
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